1. Field of the Invention
The present invention relates to a computer power supply for driving various loads using, for example, a DC output following rectification by an AC side power circuit of an AC voltage from a commercial AC power supply or a DC voltage from a DC power supply such as a battery or secondary battery.
2. Description of the Related Art
When a switching power supply with a high output capacitance (200 to 300 W) is provided in a 1 U (height 44 mm units) size as the computer power supply described above, a large number of cooling fans are used conventionally in order to extract an output capacitance of 210 W or more due to the small size, and in so doing decreases in efficiency due to internal heat loss can be avoided. In many cases, however, efficiency of only 65% to 68% or thereabouts can be achieved, and moreover, power consumption increases as the number of cooling fans rises. As a result, considerable increases in efficiency cannot be achieved, and improvements are urgently desired.
A device which is constituted such that the internal temperature is maintained at a constant level at all times by modifying the discharge rate of the cooling fan in accordance with the amount of generated heat, which varies according to the load current, has also been proposed (see Japanese Unexamined Patent Application Publication 7-231058 (FIG. 1), for example).
In the aforementioned publication, the discharge rate of the cooling fan is reduced when the load current is small, and thus efficiency can be improved slightly in comparison with a device in which a large number of cooling fans are all driven. However, this device does not provide an ultimate solution.